Dry etching is the most important technology for patterning insulating films, wiring materials, etc. in the manufacture of semiconductor devices. In the dry etching process a pattern is formed on a substrate, deposited by sputtering, CVD, spin coating, etc., by applying, exposing and developing a photoresist; after which the insulating film and the wiring pattern are formed by dry etching using a reactive gas and said photoresist as mask. After this patterning, ashing is performed, and the resist residues, which still remain in part after the photoresist used as mask has been removed by ashing, are typically removed by a stripping liquid.
However, the photoresist residues which remain after dry etching cannot be completely removed by the combination of an organic solvent with alkanolamine generally used as conventional stripping liquid (e.g., JP, A, 5-281753; U.S. Pat. No. 5,480,585). It is thought that the reason for this is that, together with the etched material, part of the resist residues remaining after ashing becomes inorganic. Therefore, stripping liquids containing fluorine compounds (JP, A, 7-201794; EP, A, 662705), hydroxylamine (U.S. Pat. No. 5,334,332) and quarternary ammonium compounds (JP, A, 8-262746; U.S. Pat. No. 5,567,574) have been proposed for removing photoresist residues after dry etching. However, since these stripping liquids corrode the wiring material, it is necessary to rinse with isopropyl alcohol or another organic solvent and to perform the treatment at a high temperature to remove resist residues completely.
Moreover, the impact of organic compounds on the environment has to be taken into consideration, since these stripping liquids are prepared from some 10% to 100% of organic compounds and since rinsing with organic solvents is also necessary.
On the other hand, together with the diversification of materials used for semiconductor devices in recent years, brought about by the use of new metallic materials such as barrier metals, ferroelectrics, etc. as wiring materials, etc., a diversification of the contents of the photoresist residue remaining after dry etching has also taken place. What is required of the removing liquid is that it be effective in removing photoresist residues and that it does not corrode the surrounding materials.
Also, the use of the before-mentioned fluorine compounds and inorganic acids is subject to limitation, since they possess the characteristic of etching lead zirconium titanate (PZT), which is a ferroelectric material. Moreover, removing methods using strongly alkaline liquids, such as tetramethylammoniumhydroxide (TMAH), etc., have also been proposed (JP, A, 8-222574); however, alkaline liquids cannot be used with titanium nitride, one of the barrier metals which is easily etched on the alkaline side, nor with hydrogen silsesquioxane (HSQ), which recently received much attention as interlayer insulating film because of its low dielectric constant, since there is the danger of film degradation (increase of the dielectric constant when the Si--H group changes to Si--OH). I.e., TMAH cannot be used with semiconductor devices in which PZT occurs together with titanium nitride or HSQ.
Thus, considering that the stripping liquids of the prior art are limited depending on their intended purpose, there is a need in the future for combining stripping liquids corresponding to the properties of the different materials used in the manufacturing processes of semiconductor devices. Therefore, when treating laminated films in which different materials are stacked, a different stripping liquid tank is required for each material; however, from the point of view of the manufacturing processes, production line planning and operating costs, this is a very negative factor.
Moreover, a related invention is mentioned in JP, A, 10-256210; however, the publication date of this application is Sep. 25, 1998, which is after the filing date of Feb. 27, 1998 of Japanese Patent Application Hei. 10-62031 which is the application on which the priority rights of the present application are based.